Document Type
Journal Article
Publication Title
Process Safety and Environmental Protection
Volume
185
First Page
64
Last Page
75
Publisher
Elsevier
School
School of Engineering
Funders
National Key R&D Program of China / Beijing Zhong Dian Hua Yuan Environment Protection Technology Co., Ltd. / Ningbo Science and Technology Innovation Key Projects / Ningbo Municipal Commonweal Key Program / S&T Program of Hebei / Mineral Resources Analytical and Testing Center, Institute of Process Engineering, Chinese Academy of Science
Abstract
This paper reports an enhanced approach of thermal reduction of phosphogypsum (PG) in the presence of sodium chloride (NaCl) in its molten phase. The thermodynamic together with in-situ thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) result indicates the yield of CaS (solid) at the investigated temperature range (800–850 °C). Addition of NaCl not only appreciably reduces the activation energy of this reaction (800–850 °C) on average from 315 to 175 (kJ·mol−1) materially, but also significantly improve the conversion from CaSO4 to CaS. Additionally, the NaCl based waste salt (NaCl-WS) containing organic compounds (0.21 wt%) was found to produce similar results when compared with the pure NaCl addition at investigated temperature range. The optimal conditions via parametric optimization: i.e., 800–850 °C, 15 wt% (NaCl-WS), and 6 (ratio of PG/C (carbon) wt/wt), were determined. The mechanistic study together with using density functional theories (DFT) shows that the synergistic effect by NaCl addition was caused by the coupled-vacancy diffusion mechanism when NaCl melts at high temperature and C atom shows proximity to oxygen (O) atom from the SO42- cluster in the CaSO4 crystallite structure. The evaluation of the process shows appealing advantages over the conventional PG thermal reduction. By carefully manipulating temperature range together with the NaCl-WS addition, the proposed new process simultaneously realizes PG thermal reduction and environmental utilization of NaCl-WS.
DOI
10.1016/j.psep.2024.03.007
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Comments
Chao, L., Xuebin, A., Hu, J., Wang, Y., Wang, S., Wang, Y., . . . Sun, Y. (2024). Enhanced phosphogypsum thermal reduction by carbon in presence of sodium chloride at high temperature. Process Safety and Environmental Protection, 185, 64-75. https://doi.org/10.1016/j.psep.2024.03.007